1. Field of the Invention
This invention relates to annular disc brake systems operating in a fluid environment. More specifically this invention relates to providing a braking system that allows circulation of lubrication and cooling fluid through the use of machined fluid passages in the system annular piston and the system outboard brake ring.
2. Description of the Prior Art
Wheel brakes carried on axles residing in a fluid bath are in contemporary use on vehicles such as farm and construction machinery. Typically agricultural and industrial tractors are equipped with inboard brakes for the rear axle. These inboard brakes may be disc brakes which operate in a fluid bath also serving as a source of fluid for hydraulic components of the tractor as well as a lubricant for the differential. Such brake systems utilize an annular piston to apply pressure to a disc which is splined to an axle or a planetary drive shaft. The opposite face of the disc adjoins the stationary outboard brake ring and is in contact with it during braking. Frictional surfaces on opposite sides of the disc having a lining of microscopically porous paper-like material bonded thereto. While the brake disc will generally have a splined central aperture compatible with the splines on the vehicle drive axle or planetary drive shaft. In addition to the central aperture it is usual to find a plurality of radially disposed apertures in the brake disc between the splined central aperture and the frictional surface or lining on the disc which allow fluid to pass from one side of the disc to the other side of the disc thus allowing the benefit of cooling fluid to reach the frictional surface on either side of the disc. To enhance the utility of the apertures the brake disc might also be equipped with an oil baffle ring to assist in delivery of cooling fluid to the lining material.
Through normal braking the heat buildup in the lining material is significant. The fluid bath in which the brake operates will generally work with the brake disc to provide a media to dissipate heat from the lining material. However, there are extreme instances where the brake disc will be rotating through the fluid bath at such a rate that it is difficult to maximize the transfer of heat between the lining material of the brake disc and the fluid bath. In these instances it has been found that increased lubrication and cooling effectiveness can be attained if fluid from the fluid bath can be pumped to and over the frictional surface of the disc.
A more conventional brake system provides cooling and lubricating oil to the lining material by either dipping the friction material into the fluid and/or the more costly means of causing the fluid to flow across the lining material surface by a forced or pressurized lubrication system. The means provided by this invention strives to improve a heat transfer between the lining material and the cooling fluid by increasing the opportunity of fluid circulation from the fluid sump to the outer periphery of the brake disc.
Contemporary state of the art of fluid environment brake systems generally do not provide for sufficient circulation of fluid to ensure optimum cooling and lubrication of the brake disc lining material.
The major object of this invention is to improve the dissipation of heat in a wet disc brake system by improving the circulation of cooling fluid.